Light-emitting apparatus and production method thereof

ABSTRACT

A light-emitting apparatus can prevent a shadow mask from contacting a light-emitting medium to suppress damage of the medium, by using a conductive layer formed on a device isolation layer as a pressing member for the shadow mask, and can attain more secure conduction between a second electrode and an auxiliary electrode. The apparatus can be formed by forming first and auxiliary electrodes on a substrate; forming a device isolation layer between the first electrodes and forming an opening on each of the first and auxiliary electrodes; forming a conductive layer on the device isolation layer to cover the openings above the auxiliary electrodes; bringing a shadow mask into contact with the conductive layer and forming a light-emitting medium in a thickness smaller than the thickness of the conductive layer; and forming a second electrode to cover the light-emitting medium, the device isolation layer, and the conductive layer.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/939,733, filed Nov. 14, 2007, the content of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention belongs to the field of technology of alight-emitting apparatus including a light-emitting device and aproduction method thereof.

2. Description of the Related Art

An organic electroluminescent device utilizing electroluminescence(hereinafter, simply referred to as EL) of an organic material hasattracted attention as a light-emitting device which can emit light at ahigh luminance by low-voltage driving.

A display apparatus of an active matrix type using such an organic ELdevice (i.e., organic EL display) is provided with a thin filmtransistor (hereinafter, simply referred to as TFT) in each of pixelsformed on a substrate. The organic EL device is formed on an interlayerinsulating film formed so as to cover the TFTs.

The organic EL device has a first electrode patterned for each of thepixels in a state of being connected to the TFTs and an insulatingdevice isolation layer which exposes the central portion of the firstelectrode as a pixel opening and cover the peripheral portion thereof.The device is configured to further include an organic layer provided onthe first electrode in the pixel opening isolated by the deviceisolation layer, and a second electrode provided in a state of coveringthe organic layer. Of the electrodes, the second electrode is usuallyformed so as to cover a plurality of pixels, and is used commonly forthe plurality of pixels.

In the organic EL device configured as described above, organic layerscorresponding to each color are formed in the same stack structurewithin the pixel opening surrounded by the device isolation layer by useof several kinds of shadow masks, so that high mask alignment accuracyis required. In general, when an organic layer is formed by vapordeposition with a shadow mask, several kinds of shadow masks are pressedagainst to the device isolation layer, organic layers are formed into astack film.

Further, in such an active matrix type display apparatus, in order tosecure a pixel aperture ratio of the organic EL device, it is effectiveto adopt the so-called top emission structure in which light isextracted from the side opposite to the substrate. Hence, the secondelectrode is required to be small in thickness to secure lighttransmittance, whereby the resistance value increases to makes it easyto cause a voltage drop.

Hence, a configuration is proposed, in which an auxiliary electrode madeof a metal material with good conductivity is formed, and the auxiliaryelectrode is connected to a second electrode, thereby preventing thevoltage drop of the second electrode. In Japanese Patent ApplicationLaid-Open No. 2002-318556, there is proposed a configuration in which anauxiliary electrode is formed in the same layer as a first electrode, anorganic layer is then formed on the first electrode, after which asecond electrode is formed, and the auxiliary electrode is thenconnected to the second electrode. Further, in Japanese PatentApplication Laid-Open No. 2003-316291, a configuration is proposed inwhich an auxiliary electrode is formed on a bank, an organiclight-emitting medium is then formed, and thereafter a second electrodeis formed, and the auxiliary electrode is then connected to the secondelectrode.

As described above, when the organic layer is formed by vapor depositionusing the shadow mask, organic layers are formed into a stack film withseveral kinds of the shadow masks being pressed against the deviceisolation layer. However, there has been a problem that at that time,the thus formed organic layers are damaged by the shadow masks to reducethe production yield.

However, although the display apparatus and the production methodthereof as proposed in Japanese Patent Application Laid-Open No.2002-318556 are configured to be capable of preventing the voltage dropof the second electrode, the above described problem is not yet solved.

Further, in the light-emitting apparatus and the production method asproposed in Japanese Patent Application Laid-Open No. 2003-316291, sincethe film deposition of the organic light-emitting medium is performedwithout bringing the mask into contact the substrate side, there areproblems such that the film thickness of each pixel varies and a shiftof the alignment is produced due to the bending of the mask. Further,there are also the problems that a film of the organic light-emittingmedium is deposited on the auxiliary electrode to interrupt theelectrical conduction between the auxiliary electrode and the secondelectrode, or the resistance value increases due to the organiclight-emitting medium, so that the function as the auxiliary electrodecannot sufficiently be exhibited.

SUMMARY OF THE INVENTION

The present invention provides a light-emitting apparatus which canprevent a shadow mask from contacting a light-emitting medium to therebysuppress a damage of the light-emitting medium, by using a conductivelayer formed on a device isolation layer as a pressing member for theshadow mask, and at the same time, can attain more secure conductionbetween a second electrode and an auxiliary electrode.

The present invention has been accomplished to solve the problems of theabove described background art, and the production method of alight-emitting apparatus according to the present invention is a methodof producing a light-emitting apparatus including a plurality oflight-emitting devices each including a first electrode, alight-emitting medium, and a second electrode provided in the mentionedorder on a substrate; a device isolation layer formed between theplurality of light-emitting devices and defining the respectivelight-emitting devices; and an auxiliary electrode formed between thesubstrate and the device isolation layer, which includes: forming afirst electrode and an auxiliary electrode on a substrate, forming adevice isolation layer between the plurality of first electrodes andforming an opening on each of the first electrode and the auxiliaryelectrode, forming a conductive layer on the device isolation layer soas to cover the opening above the auxiliary electrode; bringing a shadowmask into contact with the conductive layer and forming a light-emittingmedium in a thickness smaller than the thickness of the conductivelayer; and forming a second electrode so as to cover the light-emittingmedium, the device isolation layer, and the conductive layer.

Further, the light-emitting apparatus according to the present inventionincludes: a substrate; a plurality of light-emitting devices formed onthe substrate, each light-emitting device including a first electrode, alight-emitting medium patterned for each of the plurality oflight-emitting devices, and a second electrode continuously formed so asto extend over the plurality of light-emitting devices, provided in thementioned order on the substrate, a device isolation layer formedbetween the plurality of light-emitting devices and defining therespective light-emitting devices; an auxiliary electrode formed betweenthe substrate and the device isolation layer; and a conductive layerformed on the device isolation layer, the conductive layer being inelectrical conduction with the auxiliary electrode through an openingformed in the device isolation layer, and the second electrode and theauxiliary electrode being in electrically conduction with each otherthrough the conductive layer, wherein the thickness of the conductivelayer is larger than the thickness of the light-emitting medium.

According to the present invention, the conductive layer reaches anupper end planarizing portion of the device isolation layer, and thethickness of this upper end planarizing portion is formed thicker thanthe distance between the first electrode and the second electrode in alight-emitting region. The light-emitting medium is deposited bypressing the shadow mask on the conductive layer, so that no damage isgiven to the light-emitting medium and the production yield can beimproved. Further, the light-emitting medium is deposited by pressingthe shadow mask on the conductive layer, so that the second electrodeand the auxiliary electrode can be more securely in electricalconduction.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a schematicconfiguration of a display region in a display apparatus of the presentinvention.

FIG. 2 is a schematic cross-sectional view illustrating a schematicconfiguration of an organic EL device in a display apparatus of thepresent invention.

FIG. 3 is a schematic cross-sectional view illustrating an outline of aproduction step of a display apparatus of the present invention.

FIG. 4 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

FIG. 5 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

FIG. 6 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

FIG. 7 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

FIG. 8 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

FIG. 9 is a schematic cross-sectional view illustrating an outline of aproduction step of the display apparatus of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The light-emitting apparatus according to the present invention includesa plurality of light-emitting devices each including a first electrode,a light-emitting medium, and a second electrode in the mentioned orderon a substrate, a device isolation layer formed between the plurality oflight-emitting devices and defining the respective light-emittingdevices, and an auxiliary electrode formed between the substrate and thedevice isolation layer.

Hereinafter, an embodiment of a light-emitting apparatus and itsproduction method according to the present invention will be describedin detail with reference to the drawings. However, the present inventionis not limited to the present embodiment.

First, a production method of the light-emitting apparatus will bedescribed.

As shown in FIG. 3, on a substrate 101 such as a glass substrate, TFTs200 are formed. In the figure, reference numeral 102 denotes a sourceregion, reference numeral 103 a drain region, reference numeral 104Poly-Si, reference numeral 105 a gate electrode, reference numeral 106 agate insulating film, reference numeral 108 a drain electrode connectedto the drain region, and reference numerals 107, 109 insulating filmscovering the drain electrode. Incidentally, the TFT 200 is not limitedto an illustrated top gate type, and may be a bottom gate type.

To level unevenness generated on the substrate surface due to formationof the TFTs 200, a planarization layer 110 is formed on the substrate.In this case, for example, a positive photosensitive polyimide is coatedon the substrate by a spin coating method, and pattern exposure isperformed by an exposure device, and subsequently, image development isperformed by a developing device, and after that, a post baking isperformed.

First electrodes 300 and auxiliary electrode 400 are formed on theplanarization layer 110. The auxiliary electrode 400 is formed so as toextend longitudinally or transversely in a light-emitting region formedby the plurality of light-emitting devices arranged. Hence, theauxiliary electrode is preferably configured to be formed in a stripe orlattice shape along the arrangement direction between the light-emittingdevices arranged. Here, on the planarization layer 110, an Al film as areflective layer is formed in a thickness of 100 nm, and a film of aconductive oxide material (for example, ITO) is formed in a thickness ofapproximately 20 nm by a sputtering method. Subsequently, by etchingusing a resist pattern formed by an ordinary lithographic technology asa mask, the metal material layer and conductive oxide material layer arepatterned to thereby form the auxiliary electrode 400. Although in thepresent embodiment, the first electrode and the auxiliary electrode areformed on the same plane, the first electrode and the auxiliaryelectrode may be formed in different layers.

As shown in FIG. 4, as the device isolation layer 330, for example, aSiO₂ film is formed in a thickness of approximately 300 nm by using aCVD method. After that, as shown in FIG. 5, the SiO₂ film is patternedby etching using a resist pattern formed by using a lithographictechnology as a mask. At this time, the etching is performed under suchconditions that the etched side wall has a tapered shape. As a result,pixel opening portions where the center portion of the first electrode300 is exposed and contact holes (openings) of the auxiliary electrode400 are formed. In the region in which the pixel opening portion isformed, a light-emitting device is formed. That is, a plurality oflight-emitting devices are defined by the device isolation layer.

Subsequently, as shown in FIGS. 6 and 7, conductive layers 410 are eachformed so as to reach up to the upper flat surface portions of adjacentparts of the device isolation layer 330 from the contact hole and have athickness on the upper flat surface portion which is larger than thedistance between the first electrode 300 and the second electrode 320.In the present embodiment, by using a shadow mask 501, an Al film isformed in a thickness of 400 nm by use of a vapor deposition method. Atthis time, the plurality of conductive layers 410 are formed distantfrom one another each in a dot shape. This is because the formation ofthe conductive layers 410 on the device isolation layer 330 in a stripeor lattice shape is difficult. When the conductive layers are to beformed in a stripe or lattice shape, patterning using a mask isordinarily adopted. However, because it is extremely difficult to form amask opening in a stripe or lattice shape, sufficient alignment accuracycannot be obtained. Hence, by depositing a patterned film by using amask with a dot-shaped opening, the electrical conduction between theauxiliary electrode and the second electrode is secured whilemaintaining sufficient alignment accuracy.

Incidentally, although the conductive layers 410 are formed by the Alvapor deposition using the shadow mask, the conductive layers may beformed by a sputtering method or etching using a photoresist process.

Then, as shown in FIG. 8, a light-emitting medium 310 is pattern-formedso as to cover the first electrode 300 exposed in the pixel openingportion. At this time, in a state in which a shadow mask 502 abuts onthe conductive layer 410, the light-emitting medium 310 is deposited.Therefore, the light-emitting medium 310 is not damaged, so that theproduction yield can be improved. Further, there is caused nointerruption of the electrical conduction between the conductive layer410 and the second electrode 320 due to adhesion of the light-emittingmedium 310 to the conductive layer 410, so that better electricalconnection can be achieved. Further, because the conductive layer 410 isformed in a recessed manner by following the shape of the contact hole(opening) formed in the device isolation layer 330, the electricalconnection between the conductive layer 410 and the second electrode 320is achieved at the recessed portion and not hindered by the filmdeposition of the light-emitting medium 310.

Next, as shown in FIG. 9, a second electrode 320 is formed so as tocover the light-emitting medium 310, the device isolation layer 330, andthe conductive layer 410. As a result, the second electrode 320 isconnected to the auxiliary electrode 400 through the conductive layer410. Here, as the second electrode 320, for example, an In—Zn—O basedtransparent conductive film (IZO) which is a transparent conductive filmis formed in a thickness of approximately 200 nm.

Next, the configuration of the light-emitting apparatus obtained by theabove described production method will be described.

The light-emitting apparatus of the present embodiment is a displayapparatus of an active matrix type in which organic EL devices arearranged as the light-emitting devices.

As shown in FIG. 1, the light-emitting apparatus is formed such that theTFTs 200 are formed at positions corresponding to the respective pixelson the substrate 101, and the planarization layer 110 is formed so as tocover the TFTs 200. At the pixel opening portions surrounded by thedevice isolation layer 330 on the planarization layer 110, there areformed organic EL devices having the first electrode 300, thelight-emitting medium 310, and the second electrode 320 stacked in thementioned order.

In the present display apparatus, the auxiliary electrode 400 is formedon the same layer as the first electrode 300, between adjacent pixels,that is, between the device isolation layers 330, 330, and the auxiliaryelectrode 400 is electrically connected to the second electrode 320through the conductive layer 410. Therefore, the transparent conductivefilm constituting the second electrode 320 can be made thin, and yeteven when the area of the image display portion is enlarged to attain alarge area screen, lowering of the response speed and increase of thepower consumption of the organic EL device due to increase of theresistance value can be prevented. Further, the in-plane potentialdistribution can be suppressed to eliminate variation of luminance.

Particularly, the conductive layer 410 reaches the upper flat surfaceportion of the device isolation layer 330 from the contact hole of theauxiliary electrode 400, and the thickness of the part thereof on theupper flat surface portion is made larger than the distance between thefirst electrode 300 and the second electrode 320. Hence, as describedabove, when the shadow mask is pressed against the conductive layer 410and the light-emitting medium 310 is deposited in a film, the productionyield can be improved without damaging the light-emitting medium layer310.

Moreover, when the area of the display portion of the display apparatusis enlarged to attain a large area screen, because the contact of acolor filter or a sealing substrate with the pixel can be prevented, theproduction yield can also be improved without damaging the pixel.

The auxiliary electrode 400, as described above, is formed on the samelayer as the planarization layer 110, that is, the first electrode 300,and for example, is continuously arranged in a mesh shape between thepixel opening portions which are arranged in a matrix pattern on thesubstrate 101, while being insulated from the first electrode 300.Further, the auxiliary electrode 400 is connected to the conductivelayer 410 through the contact hole formed between adjacent deviceisolation layers 330, 330.

The auxiliary electrode 400 is preferably formed of, for example,aluminum or an alloy of aluminum with titanium, scandium, niobium,copper or silicon. Alternatively, the auxiliary electrode 400 may beformed of a single substance of titanium, titanium nitride, tantalum,tungsten, or molybdenum, or an alloy or a stack film of the substances,and may be constituted of the same material as the first electrode 300.

The conductive layer 410 reaches the upper flat surface portion of thedevice isolation layer 330 from the contact hole of the auxiliaryelectrode 400, and the thickness of the part thereof on the upper flatsurface portion is made larger than the distance between the firstelectrode 300 and the second electrode 320 in the light-emitting region.At this time, the material, contact area, thickness or the like of theconductive layer 410 is set so as to give a resistance value enough toattain electrical conduction between the auxiliary electrode 400 and thesecond electrode 320.

The conductive layer 410 is preferably formed of a conductive materialwhich has a good contact property with a conductive materialconstituting the second electrode 320 and also has a small resistivity.Specifically, the conductive layer 410 may preferably be formed ofaluminum; an alloy of aluminum with titanium, scandium, niobium, copperor silicon; a single substance of titanium, titanium nitride, tantalum,tungsten, or molybdenum; or an alloy or a stack film of thosesubstances.

Incidentally, in order to improve the coverage of the conductive layer410 and not to generate a crack in a step portion, it is desirable towork end portions thereof in a tapered shape.

Further, the thickness of the conductive layer 410 is preferably largerthan the distance between the first electrode 300 and the secondelectrode 320 not only at the upper flat surface portion of the deviceisolation layer 330 but also at the upper inclined surface portion.

The other constituent members are configured to be the same as theordinary light-emitting apparatuses.

When the first electrode 300 is used as a cathode and the secondelectrode 320 is used as an anode, the first electrode 300 is formed ofan alloy or a compound of a Group 1 or 2 element of the periodic table,and is formed of aluminum or silver, or an alloy of aluminum orneodymium. Alternatively, there may be used a composite layer obtainedby stacking, on the above-mentioned reflective electrode, a layer ofindium tin oxide, zinc oxide, zinc oxide added with gallium, or acompound thereof.

The second electrode 320 is formed of indium tin oxide, zinc oxide, zincoxide added with gallium, or a compound thereof. In order to bring thesecond electrode 320 and the light-emitting medium 310 into good contactwith each other, a thin metal layer (not shown) may be provided at aboundary thereof.

When the first electrode 300 is used as an anode and the secondelectrode 320 is used as a cathode, the first electrode 300 is formed ofindium tin oxide, zinc oxide, zinc oxide added with gallium, or acompound thereof, or a conductive material having a work functionequivalent to those of the above-motioned substances. Alternatively, thefirst electrode 300 is formed of an alloy or a compound of a Group 1 or2 element of the periodic table. For example, there may be used acomposite layer obtained by stacking, on a reflective electrode formedof aluminum or silver, or an alloy of aluminum or neodymium, a layer ofindium tin oxide, zinc oxide, zinc oxide added with gallium, or acompound thereof.

The second electrode 320 is formed of an alloy or a compound of a Group1 or 2 element of the periodic table, and is preferably formed of analloy of aluminum or silver. However, to allow the second electrode 320to have light transmittance, it may be made extremely thin, and stackedwith a transparent conductive film such as indium tin oxide.

Further, there may be provided, under the metal material layer, aconductive oxide material layer serving as an adhesive layer with theunderlying planarization layer 110, thereby realizing a three layerstructure in which the metal material layer is interposed between theconductive oxide material layers.

The light-emitting medium 310 has a configuration obtained by suitablycombining a hole injecting/transporting layer on an anode side, anelectron injecting/transporting layer on a cathode side, alight-emitting layer, and the like. The hole injecting/transportinglayer or the electron injecting/transporting layer may be a combinationof a material excellent in efficiency of injection of holes/electronsfrom an electrode and a material excellent in transportability(mobility).

As shown in FIG. 2, the light-emitting medium 310 is constituted of, forexample, three layers of a hole transporting layer 311, a light-emittinglayer 312, and an electron-transporting layer 313, but may beconstituted of the light-emitting layer 312 only, or may be constitutedof a plurality of layers such as two or four layers. The thickness ofthe light-emitting medium is made smaller than the thickness of theconductive layer. Thereby, the light-emitting medium can be deposited infilm without contacting the mask. Particularly, in a case of alight-emitting apparatus having a plurality of light-emitting devices ofdifferent emission colors, and when a plurality of layers are formed byusing a plurality of shadow masks with different mask opening patterns,the effect of avoiding contact of the light-emitting medium with themask is very advantageous.

For the hole transporting layer 311, for example, NPD is used, but othermaterials may be used.

The light-emitting layer 312 is provided for each emission color, and isseparately deposited by use of a shadow mask. When a display apparatuswhich emit the colors of RGB is configured, as a red-light-emittinglayer, for example, CBP doped with Ir(piq)3 is used. As agreen-light-emitting layer, for example, Alq3 doped with coumarin isused, and as a blue-light-emitting layer, B-Alq3 doped with Perylene isused. However, other materials may also be used.

For the electron-transporting layer 313, for example, Bathophenantrolinehaving electron acceptability is used, but other materials may also beused.

The device isolation layer 330 is an insulating film provided betweenadjacent pixels and is formed so as to cover the peripheral edge portionof the first electrode 300, and between adjacent device isolation layers330 is formed a contact hole of the auxiliary electrode 400. The deviceisolation layer 330 is formed of an inorganic insulating film such assilicon nitride, silicon oxide, silicon oxynitride, and the like, anorganic insulating film such as acrylic resin, polyimide resin, novolacresin, and the like.

In order to prevent deterioration by moisture from the outside, a glasssubstrate (not shown) is bonded to the substrate 101 by using a UVcurable epoxy resin in a nitrogen atmosphere at a temperature below adew point of −60° C. On the organic EL device side of the glasssubstrate, a moisture absorbing film such as strontium oxide or calciumoxide is preferably formed. Further, although in the presentconfiguration, sealing is performed by using a glass substrate, thesealing may be performed by using an inorganic insulating film such assilicon nitride, silicon oxide, silicon oxynitride, and the like.

Further, in place of the glass substrate, a color filter may beprovided, and a coloring layer corresponding to each device and aprotective film may be formed. At that time, the device is preferablyprotected from the glass substrate and the color filter by means of theconductive layer 410.

The light-emitting apparatus according to the present invention can beapplied to the display apparatus as a whole which is required to beelectrically connected such as the organic EL display apparatus, theinorganic EL display apparatus, and the like. Further, as a displayapparatus, the present light-emitting apparatus can be preferably usedfor a television receiver, a monitor of a computer, a display of amobile phone, a display of a personal digital assistant (PDA), a displayof a portable audio player, a rear surface display of an imagingapparatus, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Applications No.2006-311252, filed Nov. 17, 2006, No. 2007-280166 filed Oct. 29, 2007which are hereby incorporated by reference herein in their entirety.

What is claimed is:
 1. A light-emitting apparatus comprising: asubstrate; a plurality of light-emitting devices formed on thesubstrate, each light-emitting device including a first electrode, alight-emitting medium and a second electrode, provided in the mentionedorder on the substrate; an auxiliary electrode formed on the substrateand electrically connected to the second electrode; a device isolationlayer formed on the first electrode and the auxiliary electrode andhaving an opening above each of the first electrode and the auxiliaryelectrode; and a conductive layer formed on the device isolation layerso as to cover the opening above the auxiliary electrode, wherein thelight-emitting medium is formed so as to cover the opening above thefirst electrode, and wherein the thickness of the conductive layer in anupper flat surface portion of the device isolation layer is larger thanthe thickness of the light-emitting medium.
 2. The light-emittingapparatus according to claim 1, wherein the conductive layer is formedso as not to cover the opening above the first electrode.
 3. Thelight-emitting apparatus according to claim 1, wherein the conductivelayer comprises a plurality of dot-shaped members formed distant fromone another.
 4. The light-emitting apparatus according to claim 1,wherein the auxiliary electrode is formed on the same plane as the firstelectrode.